The present invention relates to a fuel injector.
German Published Patent Application No. 40 05 455 describes a fuel injector that includes a piezoelectric actuator and a valve-closure member that can be actuated by a valve needle, the valve-closure member cooperating with a valve seat surface to form a sealing seat. The valve-closure member contacts an annular sealing point on the valve seat surface, as a result of which a spray-discharge opening is sealed. When the actuator is actuated, the valve-closure member lifts off from the valve seat surface, as a result of which the sealing seat is opened and fuel is spray-discharged from the fuel injector. In this context, the flow of spray-discharged fuel is rotationally symmetrical with respect to a valve axis. Thus the fuel is spray-discharged in a rotationally symmetrical spray cone.
One disadvantage in the fuel injector described in German Published Patent Application No. 40 05 455 is that it is not possible to specify a directional distribution of the spray-discharged fuel. As a result, it is impossible in the known fuel injector to achieve a controlled non-homogeneous fuel distribution in the combustion chamber of an internal combustion engine.
In German Published Patent Application No. 44 34 892, a fuel injector is described that has two spray-discharge openings situated at varying levels with respect to a valve axis. In this manner, the fuel is spray-discharged in two discharge directions, which include varying angles with respect to the valve axis.
One disadvantage in the fuel injector described in German Published Patent Application No. 44 34 892 is that the two spray-discharge directions are fixedly prescribed by the design. In addition, the relationship of the fuel streams flowing through the two spray-discharge openings is prescribed by the design and cannot be controlled, especially during the operation of the fuel injector.
In contrast, the fuel injector according to the present invention has the advantage that it is possible to control the fuel streams of fuel jets emerging in different spray-discharge directions, and their relationship to each other.
It is advantageous if, for throttling the fuel, partial areas are provided directly at the spray-discharge opening so as to be offset on the periphery of the valve seat surface and/or the valve-closure member. In this manner, particularly effective throttling is provided.
In addition, it is advantageous if a partial area has a raised area configured on the valve seat surface and/or on the valve-closure member. As a result, when the sealing seat is opened by a first stroke of the valve needle, the fuel flow in the fuel jet throttled by the raised area is powerfully throttled in comparison to the unthrottled fuel jet. When the sealing seat is opened by a second, larger stroke of the valve needle, the throttle effect generated by the raised area is reduced, as a result of which the fuel flow of the throttled fuel jet adjusts to the fuel flow of the unthrottled fuel jet.
It is also advantageous if the valve-closure member, for the purpose of creating an interstitial space, tapers to a blunter end than the valve seat surface, so that interstitial space, with the exception of the throttling partial areas, essentially widens radially. In this way, in response to a small stroke of the valve needle, a larger fuel flow is achieved, as result of which the difference between the throttled and the unthrottled fuel jets increases.
It is also advantageous if the valve-closure member contacts a sealing point on the valve seat when the fuel injector is closed, the sealing point being configured, with respect to the direction of flow, either downstream or upstream of the throttling partial areas, it being especially advantageous if the sealing surface is situated essentially in a plane oriented perpendicular to a valve axis. As a result, the sealing effect is not achieved on the throttling partial areas; in particular, when the fuel injector is closed, the valve-closure member in the partial areas does not contact the valve seat surface, as a result of which a reliable closing of the valve is assured. In addition, the sealing surface is easy to realize in this manner.